The following disclosure relates generally to aircraft engine nacelles and associated methods of manufacture and, more particularly, to aircraft engine nacelles having engine air inlets and landing gear mounting structures.
Aircraft having aft-mounted main wings often have engines positioned near the trailing edge of the main wing to counterbalance the weight of the fuselage extending forward of the main wing. In addition, such aircraft generally have main landing gears (xe2x80x9cmain gearsxe2x80x9d) extending downward from the main wing forward of the engines to support the aircraft when on the ground. The relative positioning of the engines and the main gears in this configuration can raise a number of design problems.
One problem is the potential for foreign object damage (FOD) caused by debris kicked up by the main gear and ingested through an engine air inlet. One approach to overcome this problem has been to extend the engine air inlet forward to position the inlet aperture in front of the main gear. Another approach has been to route the engine air inlet through the wing to position the inlet aperture above the wing and shield it from the main gear. Yet another approach has been to install a screen or similar device over the inlet aperture to prevent FOD.
All of these approaches for preventing FOD have disadvantages related to aircraft weight, complexity, and drag. For example, extending the air inlet forward of the main gear increases airframe weight. Similarly, routing the air inlet through the wing not only increases airframe weight but also increases the structural complexity of the airframe. Further, providing a screen or the like over the inlet aperture has the disadvantage of increasing aerodynamic drag and reducing inlet efficiency.
Mounting the main gears to the wing can also raise a number of design problems. One problem is that the wing structure must be tailored to provide a wheel well and carry the main gear loads. This typically requires adding significant structural reinforcement around the wheel well and providing a substantial truss structure for mounting the main gear, both of which can add considerable weight to an airframe.
Another problem related to wing-mounted main gears is preventing a fuel tank puncture in the event of a main gear collapse. On most transport aircraft, the fuel tanks in the wings (xe2x80x9cwing tanksxe2x80x9d) carry most of the fuel for the aircraft. If a main gear collapses beneath a wing tank, the main gear could puncture the wing tank. This problem is typically solved by not carrying fuel over the main gear, thus providing a xe2x80x9cdry bayxe2x80x9d in this region of the wing.
The dry bay solution has a number of drawbacks. One obvious drawback is the resulting reduction in fuel capacity. Another drawback is the unfavorable effect the dry bay has on aircraft balancing characteristics. Fuel in the wing tank can often be used to favorably balance the aircraft about its center of gravity (CG). The reduction of wing tank capacity caused by the dry bay, however, may require that other methods be used to balance the aircraft about the CG. Often, these other methods involve aerodynamically trimming the aircraft, which has the unfavorable effect of increasing the aerodynamic drag of the aircraft.
The present invention is directed to engine nacelles for use with aircraft. In one embodiment, an engine nacelle for use with an aircraft wing includes an inlet having an inlet aperture positioned below the wing, an inlet wall portion extending aft of the inlet aperture, and a gear bay wall portion offset from the inlet wall portion. In one aspect of this embodiment, the inlet wall portion has an internal airflow surface configured to direct incoming air from the inlet aperture to an aircraft engine. In another aspect of this embodiment, the gear bay wall portion and the inlet wall portion at least partially define a gear bay configured to house a landing gear assembly having a wheel truck. The wheel truck can be positionable in a deployed static position offset from the engine nacelle to support at least a portion of the weight of the aircraft. In a further aspect of this embodiment, the deployed static position of the wheel truck can be aft of the inlet aperture.
In another embodiment, the aircraft wing includes a wing root portion and a wing tip portion, and the gear bay wall portion can have a first external airflow surface facing at least generally toward the wing root portion. In one aspect of this embodiment, the inlet wall portion is a first inlet wall portion and the internal airflow surface is a first internal airflow surface. The engine nacelle can further include a second inlet wall portion offset from the first inlet wall portion and having a second internal airflow surface configured to direct incoming air from the inlet aperture to the aircraft engine. In another aspect of this embodiment, the second inlet wall portion can include a second external airflow surface facing at least generally toward the wing tip portion.
In a further embodiment, a method for manufacturing an engine nacelle for use with an aircraft wing includes providing an inlet having an inlet aperture and an outlet having an outlet aperture. The method can further include extending a first side portion at least generally between a first edge portion of the inlet aperture and a third edge portion of the outlet aperture. In one aspect of this embodiment, the method also includes offsetting a second side portion from the first side portion and extending the second side portion at least generally between a second edge portion of the inlet aperture and a fourth edge portion of the outlet aperture to define a first interior portion. The method can additionally include offsetting a third side portion from the second side portion and extending the third side portion at least generally from the second edge portion of the inlet aperture toward the fourth edge portion of the outlet aperture to define a second interior portion. In a further aspect of this embodiment, the method also includes installing an engine in the first interior portion and mounting a landing gear assembly in the second interior portion.